But what's the joke? We don't find out until a 14-year-old-boy says it plainly: "I think I or other people just sort of do it as a way of mocking people who are overly sensitive about race issues."
NPR could have done the whole story in 30 seconds. But instead it spent more than five minutes trying to grapple with a wonderful yet utterly inconvenient truth for the ostentatiously liberal network: Young people just aren't as uptight about race as their parents, never mind their grandparents, are. And, by the way, the days of segregated swimming pools and neighborhoods haven't merely "yielded" to "more subtle forms of discrimination"; they've yielded to -- wait for it -- less discrimination.
No, racism hasn't vanished. And the legacy of racism still has a long half-life.
But the simple fact is "that's racist" is the sort of thing those darn kids today say to make fun of their aging Gen X and baby boomer parents.
It's also a common joke among conservatives, precisely because we're used to being called racists for the weirdest things. If I write on Twitter something about how I don't like "Obamacare," some fellow right-winger will immediately respond with some variant of "that's racist!"
And that's the joke. And the people who've spent the last few decades screaming, "That's racist," not as a punch line but as a heinously unfair accusation or in an attempt to bully people, don't seem to get that the joke is on them.